An extrusion method is generally used to process a plate material. During an extrusion process, a material may be deformed and texture of the material may be changed. It is known that texture of a material greatly influences mechanical characteristics, for example, formability of the material. Conventionally, a metallic material has its unique slip system according to its crystal structure, and formability of the metal material may vary according to whether the slip system operates. Whether the slip system operates is closely related to texture of the metal material.